海泡石基金属氧化物复合材料的合成及其光催化性能研究进展

海泡石比表面积大、孔隙率高,且表面具有一定量的硅羟基基团,这可为其负载金属氧化物如TiO2、ZnO、Fe2O3等提供更多的活性位点,因而它可以作为一种有效载体来制备具有较好吸附性和催化性的复合材料.主要介绍了海泡石基金属氧化物复合材料的不同制备方法,如溶胶-凝胶法、沉淀法、浸渍法;概述了其在提高比表面积、孔容积以及吸附性能等方面具有的优势;并综述了其在液相和气相光催化领域中的应用;介绍了其光催化性能的影响因素及最佳降解效果;最后对其作为生态环境材料的应用进行了前景展望.     

Production of Metallic Foams Having Open Porosity Using a Powder Metallurgy Approach

A technique has been recently developed to produce foamed metallic structures from dry powder blends containing a metallic powder, a polymeric binder, and a foaming agent. The blend is molded and heat-treated to foam and consolidate the material. The final properties may be tailored by varying the sintering temperature. Microstructure, chemical composition, and properties of nickel (Ni) foams sintered at different temperature are presented and discussed. The resulting material has an open cell microstructure with three levels of porosity. This structure leads to materials having low density (∼ 90% porosity) and high specific surface area. The specific surface area is reduced and the mechanical strength is increased when the sintering temperature increases.     

Study on preparation of activated mesocarbon microbeads/expanded graphite composites for electrical double layer capacitors

Electrical double-layer capacitors are now developing very fast and people put their eyes on the investigation about materials for electrodes, such as activated carbon with high surface area. One of the main ways to enhance the capacitance of porous carbonaceous materials was to improve the porosity and specific surface area. In this paper, a novel preparation process to increase the capacitance of activated carbon without changing pore structure was discussed and expanded graphite, which was usually used in the polymer material system, was used as the composite template for activated carbons. Expanded graphite with worm-like and symmetrical pores could provide good environment for activated carbon particles to touch with each other and the structure defects at the contacting sites were offset at a certain extent. The adsorption properties of activated carbons had not been changed much more after composite preparation but the capacitance of each composite had been improved greatly because that activated carbon particles were surrounded by plenty of graphite layers with better electrical conductivities. As a result, electrical double-layer capacitors made with composites had higher capacitance comparing with activate carbons themselves and had good performance under larger discharging currents.     

海泡石基金属氧化物复合材料的合成及其光催化性能研究进展

海泡石比表面积大、孔隙率高,且表面具有一定量的硅羟基基团,这可为其负载金属氧化物如TiO_2、ZnO、Fe_2O_3等提供更多的活性位点,因而它可以作为一种有效载体来制备具有较好吸附性和催化性的复合材料。主要介绍了海泡石基金属氧化物复合材料的不同制备方法,如溶胶-凝胶法、沉淀法、浸渍法;概述了其在提高比表面积、孔容积以及吸附性能等方面具有的优势;并综述了其在液相和气相光催化领域中的应用;介绍了其光催化性能的影响因素及最佳降解效果;最后对其作为生态环境材料的应用进行了前景展望。     

多孔金属比表面积的计算方法

提出了一种根据泡沫金属的孔率和孔径这两个基本参量计算其比表面积的方法.利用泡沫金属比表面积与孔率和孔径的对应数理关系,结合有关实验数据,成功地计算出了电沉积法和高压渗流铸造法制备的泡沫金属的比表面积.     

Preparation and characterization of high surface area alumina-titania solid acids

As part of a systematic study of solid acids, a series of high surface area single-phase alumina-titania mixed oxides were prepared. These materials were found to have higher surface areas, greater porosity and enhanced specific surface acidity than comparable alumina-titania solid acids reported in the literature. The thermal stability of the phases and their textural and physicochemical properties have been studied over a range of Al/Ti compositions and for calcinations up to 1000°C. The samples were characterized by differential thermal analysis-thermogravimetry, X-ray diffraction, nitrogen physisorption and X-ray photoelectron spectroscopy. Surface acidity was measured by temperature programmed desorption and in situ Fourier transform-infrared spectroscopy, using ammonia as a probe molecule. The strength and density of the acid sites were proportional to the Ti-content. This revised version was published online in November 2006 with corrections to the Cover Date.     

Influence of the experimental conditions on porosity and structure of adsorbents elaborated from Moroccan oil shale of Timahdit by chemical activation

This study records experiments undertaken to determine the suitable conditions for the use of the oil shale of Timahdit, as an adsorbent for water treatment. A simple process was proposed based on chemical activation. The preparation has been carried out by carbonization after impregnation of the precursor with phosphoric acid. The effect of different conditions of preparation on the specific surface area is discussed. These parameters are H3PO4/shale weight ratio, carbonization temperature, carbonization time and concentration of H3PO4. The properties and surface structure of the adsorbent were investigated by XPS and FT-IR. Their total surface acidity and basicity were also determined. The retention process of methylene blue (MB) by adsorbents has been studied. It was found that MHP2 and MHP7 have relatively high retention ability as compared to activated carbons.     

On the investigation of acid and surfactant modification of natural clay for photocatalytic water remediation

In this study, a series of mineral and organic acids are introduced to natural clay modification. Several analytical techniques are employed to identify the physical and chemical changes in clay. The effect of surfactants on these properties is also investigated. The samples are prepared using simple acid treatment without filtration. The alteration in surface morphology is proportional to the acid strength as evident from SEM and XRD analyses. Therefore, the treatment with mineral acid and organic acid/HNO₃ results in the formation of new layers by surface modification as depicted in SEM images, and a higher degree of suppression in characteristic XRD reflections of clay is noticed. However, the treatment with organic acids modifies the existing interlayer spacing of clay, and therefore, the XRD characteristic reflections of clay are less affected. These observations are also supported by FT-IR analysis. The surface area of modified clay is dependent on the acid strength, composition and size of counter-anion of acid. An increase in surface area and porosity is noticed after surfactant modification of HNO₃-treated clay, where the change is more prominent at the concentration higher than their respective critical micelle concentration. Thermal stability is dependent on the chemical composition and surface area of clay materials. A relatively higher absorbance is observed for modified clay materials compared with untreated clay during DRS analysis. The catalytic efficiency of modified clay materials in Eriochrome Black T degradation has been demonstrated.     

Predicting porosity of binary mixtures made out of irregular nonspherical particles: Application to natural sediments

Predicting porosity or packing density of sediments made of coarse and fine components of arbitrary geometry is critical to many science and engineering applications. Well-established analytical models for packing of spheres express porosity of the binary mixture as a function of fine-to-coarse particle size ratio. Nevertheless, the applicability of such models to natural granular materials is limited given the nonspherical and irregular nature of the particles whose packing depends on both particle size and shape. The objective of this study is to develop a model that predicts the porosity of binary mixtures made up of irregular nonspherical particles. We modified a previously developed linear sphere-packing model so that it takes into account the effect of both the particle size and shape. As an input, the modified model uses the coarse-to-fine particles specific surface area ratio instead of using the particle size ratio required by the sphere-packing model. We tested the modified model by predicting the porosities of a binary mixture composed of coarse and fine calcite aggregates. We further validate the model by using published data on the porosity of binary mixtures made of synthesized, cubical and cylindrical particles. Our model predictions show good agreement with the measured porosity.     

Preparation of titania-silica cryogels with controlled shapes and photocatalysis through unidirectional freezing

Homogeneous titania-silica binary hydrogels were molded into various shapes, microhoneycomb, self-standing bundle, microfibers, and powder, by a unidirectional freezing method. Moreover, by freeze-drying the unidirectionally frozen samples, the honeycomb walls or microfibers obtained were converted into mesoporous cryogels which possessed considerable high surface areas (up to 1057 m² g^− 1) and large mean pore diameters of 2-6 nm. Thanks to the high porosity and well-dispersed titania, the titania-silica binary cryogels exhibited very high photocatalytic activity in the decomposition of salad oil under ultraviolet irradiation.     

气凝胶在气体吸附净化中的应用研究进展

气凝胶(Aerogels)是一种以空气为介质的轻质多孔性凝聚态物质,由胶体粒子或高聚物分子相互聚集构成独特的纳米多孔三维网络结构。气凝胶的颗粒相和孔隙尺寸均为纳米量级,具有相当高的比表面积和孔隙率、可调控的开放孔隙结构、易于化学修饰的表面以及多样化的种类和形态,其气体吸附量可比同等条件下活性炭吸附量高两个数量级,因此在气体吸附净化领域逐渐受到人们的广泛关注。目前,气体吸附净化领域研究较多的气凝胶主要是SiO_2气凝胶和炭气凝胶。此外,近年来对金属氧化物气凝胶以及SiC气凝胶、石墨烯气凝胶、生物质基气凝胶等新型气凝胶的气体吸附应用也有相应的研究报道。吸附材料对目标气体需要同时具有较高的吸附容量和良好的选择性吸附能力。气凝胶的高比表面积和多孔性质提供了众多的吸附位点,但仅依靠自身物理吸附作用的吸附量有限,对目标气体的选择性不高,在实际吸附应用中,往往由于共存气体组分的竞争吸附影响对目标气体的吸附性能。因此,为了进一步提升气凝胶的吸附容量,提高对目标气体的选择性,研究人员围绕气凝胶修饰改性进行了大量的研究探索工作,并取得了一定的进展。目前,气凝胶吸附净化研究报道的目标气体主要是温室气体CO_2和大气中主要的污染物挥发性有机化合物(VOCs)。针对目标气体的不同可分别通过氨基功能化、氮掺杂等方法引入碱性位点或通过引入非极性官能团对气凝胶进行疏水改性,以提升气凝胶对CO_2或VOCs的吸附量和选择性。所采用的修饰改性方式主要有以下两种:一是在湿凝胶形成后或超临界干燥后通过嫁接、浸渍等手段对气凝胶表面进行功能化改性,通过引入特定的官能团或活性组分提升气凝胶对目标气体的吸附量和选择性;另一种是在溶胶-凝胶反应过程中引入功能化前驱体,在分子或纳米尺度上赋予气凝胶网络特定的性能,进而有效平衡活性组分稳定性和对目标气体的吸附性能。此外,对于炭气凝胶,还可通过活化进一步增大比表面积,改善孔隙结构和表面化学性质,从而实现对目标气体污染物吸附性能的优化。本文归纳了各类气凝胶在CO_2与VOCs吸附净化方面的研究进展,介绍了气凝胶的制备过程和结构特点,讨论并对比了不同气凝胶对目标气体的吸附性能与吸附机理,总结了当前气体吸附净化研究中对气凝胶进行修饰改性的主要方法,最后指出提高气凝胶的结构稳定性和吸附速率、设计可同时吸附多种目标气体的气凝胶、缩短制备周期并降低成本是未来研究工作的重点。     

以煤矸石为原料的水处理滤料的研制

研究了一种以煤矸石为主要原料,通过添加适量成型剂、膨胀剂,经高温烧结生产球型多孔轻质污水处理滤料的制造方法,并以滤料的比表面积、孔隙率为主要因子,考察原料配比、升温方式、成球时水加入量、终温及终温煅烧时间等参数对滤料理化性能的影响.结合扫描电镜分析了滤料微观结构,并对煤矸石烧结膨胀成孔机理进行了分析.通过正交试验确定了最佳工艺参数.主要配方为:煤矸石50-99%,粉煤灰0-25%,膨胀剂0.5-1.0%.所得成品滤料主要性能参数为:比表面积6.0-8.6m2/g,孔隙率40-50/%,堆密度0.9-1.1g/cm3,磨损率<2.0%,平均孔径85-190/μm.以煤矸石为原料生产球型多孔轻质污水处理滤料具有原料来源广泛、生产工艺简单、无污染、成本低、产品附加值高等特点,其生产可以利用现有水泥厂的生产设备与工艺转产.     

Corrosion of SiC fibres with HNO3

The corrosion of SiC fibres with HNO₃ has been studied. Characterization has been carried out by means of infrared spectroscopy, scanning electron microscopy and adsorption of nitrogen and benzene. Corrosion attack changes the specific surface area of the fibres and increases the surface roughness along the fibres. The microstructure of the fibres is not modified by the attack. The surface heterogeneity of the original fibres shows a different feature when the fibres have been corroded; the distribution of active sites on the surface of the fibres is changed by acid attack.     

Surface properties of bioactive TEOS–PDMS–TiO2–CaO ormosils

Tetraethyl orthosilicate (TEOS)–polydimethyl siloxane (PDMS) ormosils with different amounts of Ti and Ca were prepared and characterized. Several surface properties such as specific surface area, porosity, fractality, dispersive and polar surface energies were determined and related with their in-vitro bioactivity. It has been found a dependence of the surface fractal dimension with the concentration of Ca²⁺ ions that induce the appearance of rough surfaces. The dispersive surface energy, γ _S ^d , increased with the incorporation of Ti or Ca and the presence of micropores, but Ca(NO₃)₂ precipitates in the surface coming from non-incorporated Ca lead to a decrease of the surface energy values. In relation with the polar surface energy, it has been observed that all ormosil materials presented amphoteric character with a larger presence of base surface sites than acid ones. The basicity of the surface increased with the concentration of Ti and Ca, while the acidity decreased. The in-vitro bioactivity of the surface was estimated by soaking samples in simulated body fluid (SBF) and afterwards characterized by means of X-ray diffraction (TF-XRD) and field emission scanning electron microscopy (FE-SEM). It has been observed that in vitro bioactivity is related with the polar surface characteristics of these materials, being necessary for the bioactivity, the presence of a highly polar surface with intermediate base/acid ratio and specific roughness.     

模板法制备高比表面积的氟化镁及其在HFC-152a脱HF反应中的应用

镁基固体酸催化剂在含氟化学品的合成中具有优异的性能。利用模板法制备了高表面积的氟化镁,并考察了SiO₂模板剂的用量对其结构及催化性能的影响。通过N₂物理吸附、X射线衍射、NH₃-程序升温脱附、透射电镜和X射线光电子能谱等表征手段进行了表征, 以1,1-二氟乙烷(HFC-152a, CH₃CHF₂)脱HF制备氯乙烯(VF,CH₂=CHF)为探针对其催化性能进行了研究。结果表明, SiO₂模板剂用量对氟化镁的比表面积、晶粒度和酸性有较大影响。当SiO₂模板剂用量为14mol%时, 氟化镁比表面积可达304 m²/g, 是不添加SiO₂模板剂的2.5倍, 而且Mg晶粒度更小, 配位数更多。随着Mg配位数增多, MgF₂的酸性位急剧增多, 在以Lewis酸为活性位的1,1-二氟乙烷脱HF反应中, MgF₂的催化活性迅速升高。因此, 以SiO₂为模板是制备高活性MgF₂催化剂的有效方法。     

基于孔尺度的泡沫金属强化相变储热材料传热性能数值模拟

导热系数低是影响相变储热材料应用的主要难题之一,而泡沫金属具有高热导率、高孔隙率以及高比表面积等特性,在相变材料中添加泡沫金属可实现强化传热。该文基于泡沫金属基3D微观结构W-P模型,重点分析了泡沫金属基复合相变材料有效导热系数与泡沫金属孔隙率以及孔径的关系,采用数值模拟方法利用该模型预测并验证了泡沫铝6101添加空气与水的有效导热系数,研究结果表明该模型能够精确预测泡沫金属材料有效导热系数,在此基础上预测了石蜡中添加泡沫铜的有效导热系数,结果表明,泡沫金属可以显著提高相变材料的导热系数,当泡沫铜的孔隙率为97.57%时,复合相变材料的导热系数与纯石蜡相比提高了13倍。研究结果对于相变储热材料的热物性强化研究具有一定参考价值。     

活性炭改性研究新进展

从表面物理结构特性和表面化学性质两方面叙述了国内外在活性炭改性方面的研究进展.表面物理结构特性改性考察了增大比表面积和控制孔径分布,表面化学性质改性主要研究了氧化还原、负载金属离子以及微波改性,探讨了各种改性活性炭的优缺点和改性机理,并展望了其应用前景.     

硅溶胶中二氧化硅粒径及比表面积测定

硅溶胶中二氧化硅粒度大小与尺寸分布对其性能有重大影响，为此提出了二氧化硅粒径与比表面积应成为交的重要性能指标，并对二氧化硅粒径比表面积的测定方法做了讨论。     

The Simplified Analytical Models for Evaluating the Heat Transfer Performance of High-Porosity Metal Foams

The accurate evaluation of the specific surface area and the effective thermal conductivity (ETC) of high-porosity metal foams is an important prerequisite to study the mechanism of heat transfer enhancement. In this paper, the tetrakaidecahedron, concave triangular prism and equivalent tetrahedron were used to develop the geometry shapes of cell, ligament and node, respectively. The calculation model of the specific surface area characterized by porosity and pore density (PPI) was deduced by considering the shape characteristics. Based on the angle between the two-dimensional plane skeleton layer and the heat flow direction, the ETC analytical calculation model characterized by only the porosity in the three-dimensional space was deduced. Without any other fitting or experimental empirical parameters, these two models are only related to porosity and PPI, which are the most readily available parameters for the metal foams. The results of these models are consistent with the experimental and empirical data in other literature, indicating that these models are both versatile and accurate.     

Relation between biochar physicochemical characteristics on the adsorption of fluoride,nitrite, and nitrate anions from aqueous solution

This study describes how physicochemical characteristics of rice straw-based biochar, prepared at a different pyrolysis temperature (550, 650, 750°C) and treated by HNO₃ or H₂O₂ or KMnO₄, influence on its removal capacity for fluoride, nitrite, and nitrate anions from the water. Biochars exhibit broad pore size distribution from wide mesopores (5.0?nm) to narrow micropores (1.0?nm). Furthermore, all prepared biochars have both basic sites (2.8–8.13?meq/g) and acidic ones (1.8–9.3?meq/g) on their surface. The effect of biochar porosity, acidity, and basicity on anions adsorption was studied. KMnO₄- and H₂O₂-treated biochar give high nitrite and nitrate uptake in micropore range (0.03–0.05 cc/g) and mesopore range (0.01–0.06 cc/g) while HNO₃-treated ones give low uptake in both micropore range (0.02–0.021 cc/g) and mesopore range (0.01–0.05 cc/g). As a conclusion, no particular characteristics seem to be an influential essential in the removal of anionic contaminants. These observations are useful to guide the surface modification of biochars as efficient sorbents for specific application needs and removal of environmental pollutants.